A novel yeast for immune support in shrimp

An exploration of how P. guilliermondii in diets impacts shrimp immune physiology and performance.

By Sarah Cooper, François Jégou, Delphine Weissman and Yoav Rosen,

published in Aqua Culture Asia Pacific October 2022

Different types of yeasts and their extracts are used as feed ingredients in aquaculture because of their nutritional value and/or bioactive compounds. Saccharomyces cerevisiae is the most commonly used yeast in animal feed applications. Pichia guilliermondii is a novel yeast with unique morphology, structure and consequent activity that has recently shown potential in shrimp with regards to immune support.

A novel yeast with potential in shrimp feed

The differences in the morphology and physical characteristics of P. guilliermondii and S. cerevisiae have been assessed in a side-by-side study by Peisker et al. (2017). There are significant differences between them: P. guilliermondii yeast cell is smaller and as a result has a greater surface area to volume ratio. It is also significantly more hydrophobic compared to S. cerevisiae. Additionally, the distribution of glycoproteins in the yeast cell wall varies, suggesting that P. guilliermondii has a different cell wall structure and composition to S. cerevisiae. These particularities may be associated with significant differences in how the two yeast cells behave when used in aquafeeds.

A call for new shrimp management approaches

As shrimp lack an adaptive immune system, preventive therapies such as vaccines that are used in more immune- competent species cannot be used to protect shrimp against certain infectious diseases. Concomitantly, with growing concerns surrounding antimicrobial resistance, restrictions on the use of antimicrobials to support health in animals used for food are increasing, including shrimp production.

Consequently, alternative strategies are being sought to enhance shrimp health and performance in a sustainable way. Such alternative methods include farm management practices, bioremediation, genetics and nutrition including specialty additives.

Supporting immune physiology and improved performance in shrimp

The association between the use of P. guilliermondii in the diet of shrimp and beneficial impacts on parameters related to shrimp immune physiology and performance has been explored in a few studies.

Immune physiology

An initial study was performed in a research facility in Thailand. It evaluated changes in critical immune parameters in shrimp before and after experimental challenge with Vibrio harveyi when shrimp are supplemented with P. guilliermondii, compared to those without supplementation as shown in Figure 1.

At the end of the 28-day feeding period, shrimp from both the supplemented and control groups were sampled to measure the concentration of total and granular haemocytes. Following this, shrimp from each group were infected with V. harveyi and then 3 hours later the number of V. harveyi cells remaining in the haemolymph of each group was measured to assess the efficacy of bacterial clearance.

Whereas the level of total haemocytes remained unchanged between the two groups, the granular haemocyte count was significantly increased in the haemolymph of shrimp fed P. guilliermondii (P<0.05; Figure 1). Haemocytes are invertebrate blood (haemolymph) cells that are involved in critical shrimp immune defence processes such as coagulation and phagocytosis of invading microorganisms. Although total haemocyte count is used as an indicator of overall shrimp health status, granular haemocytes contain the primary humoral defence factors that are released during a pathogen invasion. An elevated proportion of granular haemocytes amongst total haemocytes may therefore indicate primed immune capabilities and consequently a more effective response to pathogen challenges.

The P. guilliermondii-fed shrimp, having a greater proportion of these granular haemocytes present, were then found to have a significantly lower number of V.harveyi cells remaining in their haemolymph when measured 3hours following the challenge(P<0.05;Figure2).

Improved survival when challenged

Two further studies were conducted to examine the potential impact of P. guilliermondii supplementation on performance during two common infectious challenges: white spot syndrome virus (WSSV) and Vibrio parahaemolyticus, the etiological agent of early mortality syndrome or EMS, also known as acute hepatopancreatic necrosis disease (AHPND).

Both studies took place in a wet laboratory in Peru and were similar in design, having three treatments within each study: the unchallenged control group was fed the basal diet without the supplementation of P. guilliermondii; the other two groups were both challenged, but only one of these groups received P. guilliermondii supplementation. In both studies, the groups of shrimp fed diets supplemented with P. guilliermondii had significantly improved survival compared to the challenged control groups: 84% greater survival in the WSSV challenge (P<0.05; Figure 3), and 76% greater survival in the V. parahaemolyticus challenge (P<0 .05; Figure 4).

Better growth under unchallenged conditions

The performance of shrimp fed diets supplemented with P.guilliermondii under conditions without any specific infectious challenge was assessed in two studies in the ADM research facilities in Vietnam. During each trial, eight replicates per treatment group were fed with either a basal control diet or the basal diet plus P. guilliermondii supplementation at 0.1%. The average weight gain of shrimp between the start and end of the study was significantly greater, by 9% and 10% respectively (P< 0.05; Figure 5) for the shrimp receiving the P. guilliermondii supplementation compared to shrimp fed the basal control diet.

Promoting better outcomes for shrimp production

The association between the use of the novel yeast P. guilliermondii in shrimp diets and beneficial impacts on physiological and performance parameters has been demonstrated in several studies, across different markets and under different conditions. It may be the specific morphology and unique structure of P. guilliermondii that influence these extraordinary and beneficial outcomes. As such, P. guilliermondii may represent a cost-effective, natural means of reducing the impact of health challenges and improving performance in shrimp production.

Reference

Peisker, M., Stensrud, E., Apajalahti, J., Sifri, M. 2017. Morphological Characterization of Pichia guilliermondii and Saccharomyces cerevisiae yeast and their Effects on Adherence of Intestinal Pathogens on Piglet and Chicken Epithelium In- vitro. J Anim Res Nutr Vol No 2 Iss No 1:9 doi: 10.21767/2572- 5459.100029

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Benefits of Pichia Guilliermondii in shrimp feeds

Scientific abstract: Pichia guilliermondii enhances shrimp immunity and growth